A cohort study of systemic lupus erythematosus for elucidating the association between intake of isoflavones and prognosis

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Objective: To investigate the associations of intake of soy products, isoflavones and other nutrients with the occurrences of active disease and vascular damage in female patients with systemic lupus erythematosus (SLE).Methods: Clinical and questionnaire data were collected from 279 female patients with SLE in a 1995 baseline survey. Dietary nutrients were estimated using values from the Standard Table of Food Composition in Japan, 5th edition, and disease activity was evaluated based on the Lupus Activity Criteria Count (LACC). The patients were followed over 10 years (1995-2005), and changes in disease activity and occurrences of major organ damages were determined. Using the data from 216 inactive patients whose dietary data were complete at baseline, the association of each nutrient intake with the occurrence of active disease was evaluated. The relation of diet with the development of 3 types of vascular injury (ischemic heart disease, cerebrovascular accident, thrombotic events) was examined in 196 patients who had been inactive with no prior history of these damages.Results: Among 216 inactive patients, 43 patients developed active disease during 1995-1999. The proportional hazard model including indicator variables for tertiles of each nutrient, total energy, and confounding variables revealed no significant association of intake of soy products and isoflavones with the risk of active disease, although a significant inverse association was observed for intake of some other nutrients: vitamin B6 (p for trend=0.04) and total dietary fiber (p for trend=0.0l). On the other hand, among 196 patients who had been inactive with no prior history of vascular damages, 20 patients developed vascular injury during 1995-2005. Although a modest risk elevation of vascular injury was observed at the highest tertile of soy products and genistein, the statistical test showed no linear association between intake of these nutrients and the risk of vascular injury.